Antibiotic Sensitivity Test Flashcards
Refers mostly to antibacterial agents that treats or prevents infectious diseases.
ANTIBIOTICS
Chemotherapeutic agents/antimicrobials produced by molds or bacteria
ANTIBIOTICS
isolated a strain of bacteria which lead to the development of erythromycin, a broad-spectrum antibiotic used to treat and prevent a wide range of infections.
aguilardo aguilar
Inhibition of DNA-dependent
RNA polymerase
Rifampicin
Cell membrane synthesis disruptors
Lipopeptides
RNA synthesis inhibitors
Ansamycines
Folate synthesis inhibitors
Sulfonamides
Protein synthesis (305 and 50S inhibitors)
Tetracyclines
Aminoglycosides
Macrolides
Lincosamides
Amphenicols
Pleuromutilins
Oxazolidinones
Method of evaluating the sensitivity or resistance of a pathogen to certain antibiotics.
Helps determine the type and/or dosage antimicrobials effective for treatment
ANTIBIOTIC SUSCEPTIBILITY TESTING
a solid growth medium used in microbiology to test the susceptibility of bacteria to antibiotics
Mueller-Hinton Agar
a chemical solution used to measure the number of bacteria in a liquid suspension
McFarland standard
reaction behind McFarland standard
barium chloride + sulfuric acid = barrium sulfate
white precipitate in McFarland standard
barrium sulfate
METHODS OF SUSCEPTIBILITY TESTING
Usually performed in tubes or agar
Yields quantitative result
Determines minimum inhibitory concentration or minimum bactericidal concentration.
Dilution Method
Dilution Method
Different Concentrations of Antibiotics
Incubate tubes at 37 C
16-18 h, observe which tubes are turbid
Spread Plate on Agar
Incubate tubes at 37 C
Observe for colonies
METHODS OF SUSCEPTIBILITY TESTING
Usually performed in Mueller Hinton Agar (MHA) plates as it does not inhibits a class of antibiotics called sulfonamides
Usually yields qualitative results (sensitive, intermediate, resistant)
The diameter of the zone of inhibition is measured.
The size (usually in mm) is concurred with a standard chart to interpret if the bacteria is resistant, sensitive or intermediate.
Disc-Agar Diffusion Method
Disc-Agar Diffusion Method Also known as
Also known as Kirby-Bauer Method
MHA has no PABA w/c inhibits a class of antibiotics called
sulfonamides
Disc-Agar Diffusion Method
pick 2-3 colonies
add to tube for mc farland standard
swab cotton in inoculum and to plate
antibiotic disks on plate using forceps
observe zone of inhibition
METHODS OF SUSCEPTIBILITY TESTING
used for the minimum inhibitory concentration
small amounts of antimicrobial solutions to the wells of a microwell plate and Add a bacterial suspension to each well.
Microdilution
METHODS OF SUSCEPTIBILITY TESTING
Quantitative test
Strip contains a gradient of antibiotic where MIC can be determined
E-test or Epsilometer test
brand name based on “Ilo-ilo” crediting the drugs origin
Ilotycin and Ilosone
genes that breakdown antibiotic, example penicillase
excretion channels
a process where two or more species or individuals of the same species develop escalating adaptations and counter-adaptations against each other
evolutionary arms race
competitively inhibits dihydropteroate synthase, the enzyme responsible for bacterial conversion of PABA to dihydrofolic acid
Sulfamethoxazole
blocking the production of tetrahydrofolic acid (THF), the active form of folic acid, in susceptible organisms
Trimethoprim
is a second generation fluoroquinolone that is active against many Gram negative and Gram positive bacteria. It produces its action through inhibition of bacterial DNA gyrase and topoisomerase IV
Ciprofloxacin
Inhibits the synthesis of cell walls in gram-positive and gram-negative bacteria by binding to penicillin-binding proteins
Imipenem-EDTA
nosocommial bacterial infection example mcrorg
Psuedomonas Aeruginosa
any disease contracted by a patient while under medical care
nosocomial
is known for its high level of antibiotic resistance, making it a challenging pathogen to treat. This resistance arises from multiple factors, including its low outer membrane permeability, which limits antibiotic entry, the presence of powerful efflux pumps that actively expel antibiotics, and antibiotic-inactivating enzymes that degrade the drugs before they can take effect.
Pseudomonas aeruginosa
unidirectional transfer of genes between cells that are not direct descendants of one another, meaning bacteria can share genes with other bacteria, even with other species. This method of gene transfer allows cells to rapidly adapt and respond to their environment by acquiring new characteristics, which lets bacteria form antibiotic-resistant mechanisms that they can also transfer with others.
Horizontal gene transfer
is specifically utilized for this experiment because it supports the growth of fastidious and nonfastidious organisms, the starch in the media absorbs toxins that may interfere with the antibiotic susceptibility test, and has no para-aminobenzoic acid (PABA). PABA is a vitamin-like substance synthesized by bacteria in their metabolic pathway which
Mueller Hinton Agar (MHA)
is specifically used to spread the inoculum into the agar plate as it is able to absorb a greater amount of inoculum in one dip than an inoculating loop. This ability results in a more even distribution of bacteria on the plate to prepare a lawn culture for the experiment.
Cotton swab
is particularly resistant to many antibiotics, especially those containing beta-lactams, due to its complex resistance mechanisms. Furthermore, this bacterium can form biofilms, which create a protective barrier, further enhancing its ability to withstand antibiotic treatments.
P. aeruginosa
